In some of networks used in parallel computers or the like, an optical cable is used for physically coupling a plurality of nodes with one another. There are cases in which a contaminant, such as dust or the like, enters between an optical cable and a connection unit of a rack of a computer. When a contaminant enters between the optical cable and the connection unit of the rack of the computer, the ratio at which the computer fails to receive data that has been transmitted via the optical cable increases. Thus, a link connection between nodes might be physically cut off (in other words, a link-down might occur). In some cases, even a contaminant having a size which it is not possible to visually detect causes reduction in transmission quality of a link, whereas, in other cases, reduction in the transmission quality occurs due to some other factor than a contaminant. Therefore, after the power of a part of a device, which is related to the link, is turned off, the optical cable is removed at both ends, and a port at a side surface of the device is cleaned, an operation of visually reviewing inside of a rear rack which is crowded with a cable, a water cooling kit, a power supply device, or the like, or like operation is performed. A contaminant attached to an end surface of the optical cable is removed using a special cleaner. For example, Japanese National Publication of International Patent Application No. 2015-510121, Japanese Laid-open Patent Publication No. 9-145542, or the like discusses related art.
Incidentally, after cleaning of the optical cable and visually reviewing of the inside of the rear rack have been performed, the optical cable is coupled to the computer again, the computer is started up, and whether or not the transmission quality has been improved is checked. The above-described operation considerably occurs in a site of a test, production, a product delivery destination, or the like of a parallel computer. The computer is started up after having gone through certain initialization processing, and therefore, it takes some time to start up the computer. Therefore, an operation of cleaning of the optical cable, visually reviewing of the rear rack, restarting up of the computer, or the like is a factor of increase in an operation time of a transmission test in a large-scale parallel computer. In view of the foregoing, it is preferable that reduction in operation time of a test of transmission between computers is enabled.